Biological explanations by S Laljee
- 2. Explanations – Biological vs Psychological Nature vs Nurture
- 3. Biological Explanations Genetics Bio chemicals Brain Structure
- 4. Genetics – Twin Studies • Gottesman 1991 suggests that schizophrenia is inherited through genes. Studied 40 twins - the concordance rate for MZ twins is about 48% and only about 17% for DZ twins. • Also Cardno 2002 – showed concordance rate of 26.5 MZ and 0% for DZ.
- 5. Evaluation – Twin Studies • However, the fact that the concordance rate for twins is not 100% means that Schizophrenia cannot be accounted for by genetics alone • As we already know, the higher concordance between MZ twins could be explained by greater environmental similarity rather than genetic similarity – MZ twins elicit more similar treatment than DZ twins (so can be explained by other theories) • Also the sample size of such twin studies is always going to be very small, so ……..
- 6. Further Twin Evaluation Twin studies do not all use the same diagnostic criteria – Therefore different diagnosis will produce different concordance rate. Concordance rates can also be calculated differently depending on the method used – questions the reliability of such studies.
- 7. Genetics - Adoption Studies • Tienari – 155 adopted children – who biological mothers had schizophrenia –they had a concordance of 10% compared to 1% in adopted children without schizophrenic parents. • This is very strong evidence that genetics are a risk factor for schizophrenia
- 8. Genetics – Family Studies • Gottesman also studied families – he concluded that if both your parents suffer from Schizophrenia, then you have a 46% chance of developing it yourself (compared to a 1% chance of someone selected at random will suffer) • The more genetically similar relatives are, the more concordance is found.
- 9. Family Evaluation • This evidence again strongly suggests genetics is a factor However: • It could also be explained in terms of the fact that genetically similar family members tend to spend more time together and so environment could also affect.
- 10. Biochemical Factors – The Dopamine Hypothesis • This theory claims that excessive amounts of dopamine or an oversensitivity of the brain to dopamine is the cause of schizophrenia • Eval: There is strong empirical support which suggests that dopamine plays an important role in schizophrenia – e.g drugs which block dopamine (Phenothaiazines) also seem to reduce the symptoms of schizophrenia.
- 11. The Dopamine Hypothesis - Evaluation • L-Dopa – a drug for Parkinson’s disease actually increases dopamine – this in turn can produce symptoms of schizophrenia. • Post mortems of schizophrenics, show an increase of dopamine in parts of the brain. (Seeman 1987)
- 12. Dopamine Evaluation - Negatives • Phenothiazines do not seem to work for everyone therefore.... • Cause or effect? • This theory is over simplistic and has been criticized for using the treatment to determine the cause. This is an AETIOLOGY FALLACY
- 13. Neuroanatomy - Brain Structure There is growing evidence that schizophrenia is down to physical abnormalities in the brain. Szesko et al found that the ‘asymmetry’ found in normal brains – in the prefrontal cortex is absent in people with schizophrenia.
- 14. Brain Structure People with schizophrenia have abnormally large ventricles in the brain. Ventricles are fluid filled cavities. This means that the brains of schizophrenics are lighter than normal.
- 16. Brain Structure Evidence • Andreasen et 1990 – conducted a very well controlled CAT scan study and found significant enlargement of the ventricles in schizophrenics compared to controls. • However this was only the case for men and not for women. Therefore cant generalise to everyone.
- 17. Evaluation • Research is difficult to interpret and there have been contradictory findings. • Difficult to establish cause and effect – as many participants have suffered from schizophrenia for a while and have been undergoing treatment. So.......
- 18. Further Evaluation • The main problem with such studies is that it is not found in all schizophrenics. This has lead to further research done by Crow 1985. • He suggested two types of schizophrenia with two biological causes.
- 19. Two Syndrome Hypothesis - Crow 1985 • Type one - genetically inherited associated with dopamine – characterised by positive symptoms. • Type Two – Neurodevelopmenal disorder – to do with Brain structure – characterised by negative symptoms.
- 20. Summery • Biological explanations do account for schizophrenia, however the fact that there is no conclusive explanation that accounts for all schizophrenics – psychological explanations need to be considered.
- 21. Exam Question • TASK: Exam Question: PLAN THE QUESTION • Outline and evaluate one or more biological explanations for schizophrenia. In your evaluation you should refer to research evidence. (25 marks)